1. Field of the Invention
The present invention relates to a process for the preparation of bisphenol F particulates, and, more especially, to the preparation of solid particles of bisphenol F of varying particle sizes, or degree of coarseness.
2. Description of the Prior Art
It is known to this art to prepare bisphenol F (dihydroxydiphenylmethane) by reaction between an excess of phenol with formaldehyde, such reaction typically being conducted in an acid medium. And depending upon the specific working conditions employed, the mixture obtained upon completion of the reaction contains the various isomers (2,2'-dihydroxydiphenylmethane, 2,4'-dihydroxydiphenylmethane and 4,4'-dihydroxydiphenylmethane) in varying proportions, in addition to trisphenols and products having a higher degree of condensation. It is also well known that even if the reaction is carried out utilizing a large excess of phenol, a not insignificant proportion of "heavy" products, i.e., the trisphenols and the products having a higher degree of condensation, is obtained upon completion of the reaction. The presence of these heavy products is largely responsible for the more or less pasty appearance displayed by the product obtained via the aforesaid general technique.
Moreover, since dihydroxydiphenylmethane is a useful intermediate in the manufacture of the phenolic resins, epoxide resins and especially the polycarbonate resins, numerous methods for isolating this valuable material from the mixture obtained upon completion of the condensation reaction have been proposed. However, none of the heretofore proposed methods has proved satisfactory in production on an industrial scale, because of the poor recovery yield achievable and because of the intrinsic difficulties in implementing the various proposed solutions. In the face of such problems, efforts have continued towards the production of technical-grade bisphenol F, i.e., an admixture containing about 80% by weight of the various isomers of dihydroxydiphenylmethane, as this grade appears to be quite suitable for a certain number of intended applications.
However, there then arises the problem of handling and storing such a product, which is in the form of a wax which can have a more or less pasty consistency. In fact, a product of this type can neither be converted to flakes nor be ground, since the slightest heating renders it tacky. For this reason, the users of such a starting material have no alternative but to melt this material, which is delivered in block form, at a temperature on the order of 150.degree. C., before it can be used. It will readily be seen that such a procedure is neither convenient nor without hazard. Furthermore, such a treatment can considerably increase the coloration of the product and make it unsuitable for the uses intended. It is for this reason that it has transpired to be highly desirable to be able to convert this product to a form which is easier to handle and/or to store.